1. Field of the Invention
The present invention relates to a septic tank. More specifically, the present invention relates to a septic tank for treating household waste water including human feces in daily life.
2. Description of the Related Art
Household waste water containing human feces is firstly collected in a septic tank in a basement of a building. Cleaner waste water after purification is discharged to adjacent water discharge pipes to avoid contamination to drinking water and the environment. The decayed and deposited sludge in the septic tank is removed when it is accumulated to a certain amount.
Organic nitrogen in the septic tank is decomposed by nitrobacteria into ammonia, which is then oxidized into nitrate that is less toxic. The amount of organic nitrogen contained in the discharged water is reduced to achieve the purification purposes. For purification of the waste water in the septic tank, a stirring device or pump is mounted in the septic tank for stirring or recycling the sludge, providing re-filtering and/or re-decomposition effect. However, the stirring or recycling procedure would destroy the environment for the nitrobacteria. Further, stirring and fast recycling would adversely affect the effect of decomposition and filtration, failing to purify the waste water. More specifically, the high speed recycling currents are created in the septic tank when the pump or stirring device operates. As a result, the sludge providing the environment for growth and propagation of the nitrobacteria could not effectively gather and deposit. Further, the water discharged from the septic tank is not clear enough.